It is known to provide closed circuit television surveillance systems using either cameras in a fixed location or cameras that are mounted for movement along a rail or track. It is also known, in the case of a system using a fixed-position camera, to provide automatic acquisition of a fixed target object in response to an alarm signal or the like. For example, a target object such as a door can be equipped with a sensor which provides an alarm signal to a central control portion of the surveillance system when the door is opened. Assuming that data has previously been stored in the control system to indicate the required direction of view and appropriate zoom and/or focus condition for the camera to provide an image of the target door, the control system can implement an immediate adjustment to the camera direction, zoom condition, etc. so that an image of the door is provided by the camera within a very short time after the door is opened.
However, when the system utilizes a moving camera, such as a camera mounted on a carriage which travels along a rail, the camera may be located at any arbitrary position in its range of movement at the time an alarm is received. Since the camera location at the time of the alarm cannot be known in advance, it is not possible to store in advance data defining a particular direction and zoom condition of the camera which will enable the camera to provide an image of the target from the position of the camera at the time of the alarm.
In the case of an operator-attended surveillance system, the human operator may attempt to respond to the alarm signal by operating system controls to reposition the camera carriage and to adjust the camera direction, etc. so that an image of the target object is obtained. However, the variety of possible camera positions and directions-of-view may lead to disorientation on the part of the operator. Also, if the system is set up with multiple target objects (e.g., multiple doors, windows, cabinets and so forth) for which alarms may be actuated, the operator may have difficulty identifying the particular target to which the alarm pertains. As a result, the human operator's response to the alarm may be too slow to capture an image of the event (such as entry of an intruder) which caused the alarm.
While it might be proposed to define a predetermined position along the track to which the camera should be moved in response to an alarm which pertains to a particular target, and then an appropriate direction of view and zoom condition data could also be stored for providing an image of the target from that predetermined position, such an approach carries the disadvantage that a significant amount of time may be required to move the carriage to the predetermined position from the position of the carriage at the time the alarm is received. Even if automatic camera direction and zoom adjustments are performed before or during carriage movement so that the camera will be in an appropriate orientation and zoom condition to provide the image of the target as soon as the predetermined carriage position is reached, still target acquisition cannot take place during the time the carriage is in motion, and target acquisition thus may be substantially delayed.